Marmaray, the world's deepest immersed tube tunnel
Location Bosphorus strait
Status Under construction
Start Fatih, Istanbul, Turkey
End Üsküdar, Istanbul, Turkey
Work begun 9 May 2004
Opened 29 October 2013 (projected)
Length 1.8 km
Line length 76.3 km
Operating speed 100 km/h

Marmaray is a rail transport project in Istanbul. It consists of the construction of an undersea rail tunnel under the Bosphorus strait as well as the modernization of suburban rail lines along the Sea of Marmara from Halkalı on the European side to Gebze on the Asian side. The procurement of new rolling stock for suburban passenger traffic is also part of the project.[1] Construction started in 2004, with a target opening date of October 29, 2013.[2]

The name Marmaray (Marmarail) comes from combining the name of the Sea of Marmara, which lies just south of the project site, with ray, the Turkish word for rail.


The project

The project includes a 13.6 kilometres (8.5 mi) Bosphorus crossing, the upgrade of 63 kilometres (39 mi) of suburban train lines to create a 76.3 km high-capacity line between Gebze and Halkalı and the provision of 440 rail cars.

The Bosphorus (Istanbul Strait) will be crossed by a 1.4 kilometres (0.87 mi)-long earthquake-proofed immersed tube, assembled from 11 sections, each as long as 130 metres (430 ft) and weighing up to 18,000 tons.[3] The sections will be placed down to 60 metres (197 ft) below sea level: 55 metres (180 ft) of water and 4.6 metres (15 ft) of earth.[3] This underwater tube will be accessed by bored tunnels from Kazlıçeşme on the European side and Ayrılıkçeşme on the Asian side of Istanbul. When completed, it will be the world's deepest undersea immersed tube tunnel.

New underground stations will be built at Yenikapı, Sirkeci, and Üsküdar.[4] 37 other above-ground stations along the line will be rebuilt or refurbished.[4][5] The station at Yenikapi will connect with Istanbul Metro and Istanbul LRT.[6] The above-grade suburban lines will be upgraded to three tracks, two for commuter and one for long-distance/high-speed passenger trains (bi-directional). The tunnel section allows for two, bi-directional tracks to be used by commuter and long-distance trains. During off-peak hours, freight trains may also cross the tunnel. The capacity for the suburban lines is planned for 75,000 passengers per hour in each direction.[1] Signaling must also be modernized to allow trains to be as close as two minutes apart.[7] The predicted travel time from Gebze to Halkalı is 104 minutes.[4]

Construction of the Marmaray project started in May 2004. The Marmaray tunnel was completed on the 23rd of September 2008,[8] with a formal ceremony to mark completion of the tunnel on October 13.[1] Completion of the entire project has been repeatedly delayed, and as of December 2009, was expected to occur in October 2013.[9]

After completion, the usage of rail transportation in Istanbul is predicted to rise from 3.6% to 27.7%.[5]

In February 2010, Railway Gazette International reported that the tunnel's administrators were hiring consultants to analyse options for carrying freight traffic.[10]

Rolling stock

"Marmaray EMU"
In service 2012-
Manufacturer Hyundai Rotem
Family name ICR
Formation 5/10 cars per trainset
Operator Turkish State Railways
Electric system(s) 25kV AC Overhead wires
Gauge 1,435 mm (4 ft 8 12 in) Standard gauge

Hyundai Rotem announced on November 11 2008, that it had signed a €580m contract to supply the rolling stock for the Marmaray cross-Bosporus tunnel project in Istanbul. The Korean firm saw off competition from shortlisted bidders Alstom, CAF and a consortium of Bombardier, Siemens and Nurol for the 440-vehicle contract which was placed by the Ministry of Transport's General Directorate of Railways, Harbours & Airports.[11]

The 22 m long stainless steel cars will be formed into 10 and five-car EMUs. Some production will be carried out locally by Eurotem, Hyundai Rotem's joint venture with Turkish rolling stock manufacturer TÜVASAŞ. The cars will arrive in three batches, the first 160 cars by 2011, the last by June 2014.


The project is currently four years behind schedule, largely due to the discovery of a Byzantine-era archaeological find on the proposed site of the European tunnel terminal in 2005. [12] The excavations produced evidence of the city's largest harbour, the 4th-century Port of Theodosius.[3] There, archaeologists uncovered traces of the city wall of Constantine the Great, and the remains of several ships, including what appears to be the only ancient or early medieval galley ever discovered, preventing the project from proceeding at full speed.[13] In addition, the excavation has uncovered the oldest evidence of settlement in Istanbul, with artifacts, including amphorae, pottery fragments, shells, pieces of bone, horse skulls, and nine human skulls found in a bag, dating back to 6000 BC.[3]

The suburban rail upgrade section of the project, known originally as CR1, faltered and is undergoing a re-tendering process due to attract bids in early 2011. The original CR1 consortium (AMD Rail Consortium) consists Japan's Marubeni, Turkey's Dogus Insaat and France's Alstom.

Tunnel construction is only about 18 kilometres (11 mi) from the active North Anatolian Fault, worrying engineers and seismologists. "Since AD 342, it has seen large earthquakes that each claimed more than 10,000 lives."[3] Scientific calculations to estimate the probability that at some time in the next 30 years the area will suffer an earthquake of strength 7.0 or more produced an outcome of 77 percent. The waterlogged, silty soil on which the tunnel is being constructed has been known to liquefy during an earthquake; to solve this problem, engineers are injecting industrial grout down to 24 metres (79 ft) below the seabed to keep it stable.[3] The walls of the tunnel will be made of waterproof concrete coated with a steel shell, each independently watertight. The tunnel is made to flex and bend similar to the way tall buildings are constructed to react if an earthquake hits. Floodgates at the joints of the tunnel are able to close and isolate water in the event of the walls' failure.[3]

Steen Lykke, project manager for Avrasyaconsult, the international consortium that's overseeing the construction, sums it up saying, "I can't think of any challenge this project lacks".[3]


The Japan International Cooperation Agency (JICA) and the European Investment Bank have provided major financing for the project. As of April 2006, JICA had lent 111 billion yen and EIB 1.05 billion euro. The total cost of the project is expected to be approximately 2.5 billion US dollars. As of late 2009, costs were expected to increase by approximately 500 million US dollars due to the archaeological delays.[9]


The Marmaray project has been criticized many times throughout the years by newspapers, politicians and mostly railway workers and railway enthusiasts. The criticism is due to the fact that the Marmaray project includes decommissioning the port of Haydarpaşa as well as closing İstanbul's two main railway terminals; Haydarpaşa Terminal and Sirkeci Terminal, which are both historically important as a railway station[14]. The tracks will be removed and the buildings will be turned into hotels, which has brought an uproar of rage in Turkey's railway community. Other criticisms are because of the demolition or replacement of other historically significant railway stations and railway bridges, such as Göztepe railway station. Also, it is planned to have all intercity trains terminate at Gebze and Halkalı respectively and passengers transfer to local commuter trains, which would make trains much more crowded and very uncomfortable for passengers with heavy luggage[15].

See also


  1. ^ a b c Rails under the Bosporus, Railway Gazette International 2009-02-23
  2. ^
  3. ^ a b c d e f g h Smith, Julian. "The Big Dig" Wired Magazine. Sept. 2007: pages 154–61.
  4. ^ a b c Facts and figures, web page at the Marmaray web site. Accessed on-line September 24, 2007.
  5. ^ a b Travel time and alignment, web page at the Marmaray web site. Accessed on line, 24 September 2007.
  6. ^ Istanbul Metro and LRT, web page at the Marmaray web site. Accessed on-line September 24, 2007.
  7. ^ Istanbul, web page at Accessed on line September 24, 2007.
  8. ^ Final tubes sunk on Bosphorus Tunnel, International Railway Journal, November 2008.
  9. ^ a b Marmaray completion delayed to 2013, cost increases by $500 mln, Today Zaman 2009-12-19
  10. ^ Contracts February 2010, Railway Gazette International 2010-02-09
  11. ^ Marmaray train contract signed, Railway Gazette International 2008-11-14
  12. ^ Tunnel links continents, uncovers ancient history CNN
  13. ^ Rose, Mark; Aydingün, Sengül. "Under Istanbul". Archaeological Institute of America. Retrieved 2008-10-27. ; Nautical archaeology takes a leap forward, The Times, 31 December 2007
  14. ^ Haydarpasa's protection in danger -
  15. ^ Marmaray project's negative effects on Istanbul -

External links

Coordinates: 41°1′9.42″N 28°59′48.11″E / 41.0192833°N 28.9966972°E / 41.0192833; 28.9966972

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